The practical application of .eld or natural leaching to rice straw was evaluated with the goal of improving biomass fuel
value. Observations on three rice farms in the Sacramento Valley, California indicated that potassium, chlorine and total
ash are leached from rice straw by rainfall regardless of rice variety, grain harvest method, straw arrangement, or stubble
length. Leaching of sulfur by natural precipitation was not clearly established. In selected .eld plots leached straw was
successfully collected in spring, even though biomass yields were variable (2.2–3:4 Mg h a−1) and equipment had to operate
in di6cult conditions. Total costs for collecting leached straw on an area basis ($77:07 ha−1) are 31% higher compared
to collecting crude straw in the fall ($58:67 ha−1), due to reduced performance of machinery and addition of .eld curing
operations. Analysis of historical rainfall data for the Sacramento Valley revealed that there is an 85% probability of receiving
su6cient rainfall (250 mm or more) for substantial natural leaching of straw during the winter period. The available period
for mechanized collection of rice straw after the winter period ranges from 0 to 45 days, depending on drying time needed
to accomplish favorable .eld conditions, and planting date of the next crop. The feasibility of spring collection of rice straw
could be improved if straw collection equipment were better equipped to operate under wet .eld conditions. The commercial
implementation of natural leaching of rice straw as a strategy to improve fuel quality depends on a combination of factors
that include grain harvest and straw collection practices, rainfall intensity and distribution, and .eld-speci.c factors.
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